Lactococcus lactis
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Vendhan Ramanujam M.B.B.S [2]
Synonyms and keywords: L. lactis
Overview
Lactococcus lactis is a gram-positive bacteria used extensively in the production of buttermilk and cheese[1]. This group of bacteria, previously designated as lactic streptococci (Streptococcus lactis subsp. lactis or S. lactis subsp. cremoris) was placed in this new taxon in 1985 by Schleifer.
Microbiology
Lactococcus lactis is a species of non-sporulating, non-motile, gram-positive bacteria. They are cocci that group in pairs and short chains, typically 0.5 - 1.5 µm in length. When fermenting milk, L. lactis produce large quantities of lactic acid. Cultured in the laboratory, L. lactis colonies appear bright orange on nutrient agar.
Cheese production
L. lactis subsp. lactis (formerly Streptococcus lactis[2]) is used in the early stages for the production of many cheeses including brie, camembert cheese, cheddar, colby, gruyère, parmesan, and roquefort[3]. The use of L. lactis in dairy factories is not without issues. Bacteriophages specific to L. lactis cause significant economic losses each year by preventing the bacteria from fully metabolizing the milk substrate[3]. Several epidemiologic studies showed that the phages mainly responsible for these losses are from the species 936, c2 and P335[4]. L. lactis subsp. cremoris strains are preferred over L. lactis subsp. lactis strains because of their superior contribution to product flavor via unique metabolic mechanisms[5]. The DNA sequence divergence between the subspecies is estimated to be between 20 and 30%. Of the many lactococcal strains used, L. lactis subsp. cremoris SK11 is recognized for the beneficial flavor compounds it produces.
References
- ↑ Madigan M, Martinko J (editors). (2005). Brock Biology of Microorganisms (11th ed. ed.). Prentice Hall. ISBN 0-13-144329-1.
- ↑ Chopin MC, Chopin A, Rouault A, Galleron N (1989). "Insertion and amplification of foreign genes in the Lactococcus lactis subsp. lactis chromosome" (PDF). Appl. Environ. Microbiol. 55 (7): 1769–74. PMID 2504115.
- ↑ 3.0 3.1 Coffey A, Ross RP (2002). "Bacteriophage-resistance systems in dairy starter strains: molecular analysis to application". Antonie Van Leeuwenhoek. 82 (1–4): 303–21. doi:10.1023/A:1020639717181. PMID 12369198.
- ↑ Madera C, Monjardin C, Suarez JE (2004). "Milk contamination and resistance to processing conditions determine the fate of Lactococcus lactis bacteriophages in dairies" (PDF). Appl Environ Microbiol. 70 (12): 7365–71. PMID 15574937.
- ↑ Salama, M.; Sandine, W.; Giovannoni, S. (1991). "Development and application of oligonucleotide probes for identification of Lactococcus lactis subsp. cremoris". Appl Environ Microbiol. 57 (5): 1313–8. PMID 1713027. Unknown parameter
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